APX 525/625 Generator Revision C Diagnostics
©
2005 Del Medical Imaging Corporation
7/5/2005 Page 177
The filament preheat reference voltage is sent to the Power Supply Board (124-
0108G1), where it is used to regulate the output of a feed-forward voltage regulator
circuit, which provides the regulated DC filament voltage to the primary filament
switching circuitry on the I/O Board. This voltage is also monitored on the mA/Rotor
Board (Filament Voltage Feedback), where it is compared against a threshold
comparator (U23C), which is used to detect excessive filament voltage, which could
result in filament over current conditions.
When the PREP state is active and the boost and run voltages are applied to the
stator, AC currents passing through the main and phased windings of the stator are
sampled on the I/O board by transformers T2 and T3. These transformers develop
voltages across their respective load resistors, which are sent to the mA/Rotor Board
for level and phase comparisons, to ensure proper rotor operation. Following the
boost period, the signal to step down to the run voltage is ANDed together with the
phase and level comparison signals, and the /ROTOR OK signal is generated.
The /ROTOR OK signal is sent to the Logic Board, where it is ANDed together with
the Door and Collimator Interlocks. If all the interlocks are closed and the /ROTOR
OK signal is present, the /READY LIGHT signal is sent to the Control Console, and
the generator is armed for an exposure.
Exposure Functions: (see illustration X3)
The /EXPOSE REQUEST (LOW TRUE) is decoded from serial data at the Data
Board and sent to the Logic Board (124-0096G1). Any fault condition present on the
Logic Board will inhibit or terminate the /EXPOSE Command. Any fault condition,
open interlock, or STOP signal will terminate both the /EXPOSE and /PREP
Commands. The /EXPOSE Command is then sent to several other boards:
• On the kV Regulator Board (124-0110G1), the /EXPOSE Command is used
to release the +22VDC supply voltage to the pulse transformers and enable
U7, the oscillator circuit that provides the core drive signal that will be used to
create drive pulses for the SCRs.
• On the mAs Regulator Board (124-0145G1), the /EXPOSE signal enables
U3B, a BCD counter that outputs the mAs pulses internally to the binary
comparators inside the mAs timer and outputs them to the CPU in the
Operator’s Console. The mA feedback from the high-tension transformer
assembly is used on this board for mAs timing, and then it is buffered and
sent on to the mA/Rotor board for mA control.
• On the mA/Rotor Board (124-0095G1), the /EXPOSE Command is used to
close relay K1, which changes the control of the filament drive circuit from the
preheat reference mode to actual tube current feedback mode. The buffered
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